Usher, Mary J. Blige, Gwen Stefani, Common and Train are scheduled to perform during the free Global Citizen 2015 Earth Day rally hosted by will.i.am and Soledad O'Brien. The event runs from 11 a.m. to 7 p.m. near the Washington Monument.

Earth Day organizers also are announcing plans with developers of the popular "Angry Birds'' game to create a new in-game experience about climate change. "Angry Birds'' has been downloaded 2.8 billion times worldwide. The game's climate change campaign will coincide with the U.N. General Assembly in September as world leaders tackle sustainability goals.

Earth Day Network President Kathleen Rogers says the game and celebrity power will help more people focus on solving climate change.

The rally is a joint initiative with the Global Poverty Project to end extreme poverty and coincides with meetings at the World Bank and International Monetary Fund in Washington. Top officials from the World Bank and United Nations are expected to speak at the rally.

Eliminating poverty will require solving climate change, Rogers said. So advocates on both issues are collaborating to push for sustainable international development.

"Whether it's the big migrations we expect to see or soil depletion or emptying the oceans, loss of species, loss of timberland -- all these things are creating poverty at the same time that they are also creating climate change issues,'' Rogers said.

While Earth Day is officially on April 22, the Saturday rally will ask participants to commit to making environmentally friendly "acts of green'' this year. Organizers also are asking attendees to sign petitions for a U.N. conference on climate change planned for Paris in December.

The National Park Service announced six road closures, beginning at 6 a.m. Saturday: